Gates # PL 30071. Beware, though, some here have said it's no good. I accidently abused mine I think and it split. Due possibly to running with the shim washer out of the variator. Thank god I caught it before it broke completly. Do a search for Gates in the Xciting 500 section and/or how to section with our search feature here and you'll see some more bad references to Gates and other cheaper belts. I don't think I'd use one again. Yeah, I know what you mean about the price of the OEM belts! At least I haven't broken one of those yet.
They don't have the cogs on the outer surface and I seem to remember someone here posting that the dimentions weren't quite exactly the same as OEM.
I found it by using a search feature off of the Gates website and also found local dealers that way. Called a couple of those dealers before finding one willing to order it for me. Cost was around $30.